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From the pages of 'The British Tarantula Society Journal'
BEHAVIOUR AND FEEDING IMPLICATIONS IN THE SOUTH lNDIAN
Robert Bustard and Mick Deaville
Both of us keep and breed Poecilotheria regalis. We both rear spiderlings in groups and also singly. We breed the females in separate tanks largely for convenience (ease of control). We have both sometimes left some spiderlings with the females where they were never harmed by her and we believe could be safely reared with her. This is an inconvenient method in practice due to the need to ensure adequate quantities of very small food - in a large adult's tank - for the growing spiderlings.
We have both made two observations independently which we find fascinating and which we feel should be on record. Firstly, we have found that spiderlings kept in a group show better (faster) growth than spiderlings housed separately. Secondly, we have both witnessed co-operative feeding within members of a group on several occasions. In this two or more spiderlings come together to overpower a cricket, usually a cricket that one spiderling either could not overpower itself or would be hesitant to attack alone. At no time during or subsequent to any of these observed attacks have we witnessed either spider attacking the other one, nor have spiders in the group been damaged as would occur if other siblings attacked them. Having subdued the cricket prey the spiders have pulled it into two or more pieces and each has settled down to consume its portion.
We do not suggest that the spiderlings or juveniles hunt in a co-ordinated fashion. The 'co-operative feeding' is a direct result of the social behaviour in which a group of spiderlings or juveniles are in close proximity so that other members of the group immediately see when another member catches a prey item. The fact remains, however, that as a result of co-operation they are able to successfully overcome large prey in relation to their size that a single spider could not subdue on its own. Because of their fast reactions such spiderlings may chase the food virtually simultaneously.
One of us (M.D.) has observed an agitated pyramid shape of spiderlings, on top of and surrounding one spiderling, which had caught a large (in relation to itself) prey item. It seemed as if the spiderlings were competing for all or part of the food. Even though these motions were in an obviously 'excited' predatory fashion not one spiderling was harmed? not even the unfortunate one at the bottom of the heap! Thc number of spiderlings involved was at least five - and probably more.
Spiders housed together are vulnerable at moulting times. Poecilotheria regalis housed as a group stay close together, often a number being in actual physical contact (this is equally true of juveniles housed as a group as it is of spiderlings). Yet no attacks have been recorded by us on moulting or freshly moulted spiders in the group. We are at pains to stress the group cohesion (members close together even long after the spiderling stage and in physical contact with the other members of the group). It is NOT a case of toleration, other members of the species given sufficient room for each to have their own retreats.
It is interesting to speculate how this form of social behaviour may have developed.
Suitable habitat for this spider in the wild (such as hollow limbs of trees, exfoliating bark or crevices) is probably scarce and acts to limit populations. Hence it is advantageous for those habitats that exist to be fully utilised. This situation contrasts with ground-dwelling spiders living under debris on the ground or in burrows which they excavate themselves. So the habitat preferences which have necessitated the development of tolerance to others of their kind may have, over time, led to the development of social behaviour. The Poecilotheria habitat also, of course, differs from the leaf-silk tubes of many Avicalaria species opportunities to construct these are virtually limitless.
Co-operative feeding - a direct result of the social behaviour observed - will have marked survival value in allowing the young spiders to successfully tackle bigger prey at certain seasons of the year (as is likely to be the case) there is a shortage of smaller insect prey in the habitat occupied by the spiders which they can overcome individually.
This behaviour may be a side effect of spiderlings trying to share or steal each others catches at times of food shortage in the wild but the end result is the same and it occurs in our experience without any attacks on other members of the group - even at times of 'feeding frenzies'. If this extreme tolerance towards other members of the group was not shown - even at feeding times - then this form of feeding could not have arisen as it would result in the probable death of one of the two spiders and been selected against by natural selection.
Finally, it also enhances the likelihood of observing and catching food as when one member of the group notices food other members are alerted and actively search for food.
© Copyright 'The British Tarantula Society', 1996,2007
Last Updated: April 04, 2007